From patchwork Thu Apr 10 09:23:49 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Liu Ying X-Patchwork-Id: 3960641 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 78A819F375 for ; Thu, 10 Apr 2014 09:22:13 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 785FA20632 for ; Thu, 10 Apr 2014 09:22:12 +0000 (UTC) Received: from casper.infradead.org (casper.infradead.org [85.118.1.10]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2C74620630 for ; Thu, 10 Apr 2014 09:22:11 +0000 (UTC) Received: from merlin.infradead.org ([2001:4978:20e::2]) by casper.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1WYBBL-00068E-Ru; Thu, 10 Apr 2014 09:22:03 +0000 Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1WYBBJ-0008Ad-Ji; Thu, 10 Apr 2014 09:22:01 +0000 Received: from am1ehsobe003.messaging.microsoft.com ([213.199.154.206] helo=am1outboundpool.messaging.microsoft.com) by merlin.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1WYBBF-0008A3-Ul for linux-arm-kernel@lists.infradead.org; Thu, 10 Apr 2014 09:21:59 +0000 Received: from mail64-am1-R.bigfish.com (10.3.201.238) by AM1EHSOBE014.bigfish.com (10.3.207.136) with Microsoft SMTP Server id 14.1.225.22; Thu, 10 Apr 2014 09:21:13 +0000 Received: from mail64-am1 (localhost [127.0.0.1]) by mail64-am1-R.bigfish.com (Postfix) with ESMTP id EBB864000BD; Thu, 10 Apr 2014 09:21:12 +0000 (UTC) X-Forefront-Antispam-Report: CIP:70.37.183.190; KIP:(null); UIP:(null); IPV:NLI; H:mail.freescale.net; RD:none; EFVD:NLI X-SpamScore: 0 X-BigFish: VS0(zzc89bhe0eahzz1f42h2148h1ee6h1de0h1fdah2073h2146h1202h1e76h2189h1d1ah1d2ah21bch1fc6h208chzz1de098h8275bh8275dh1de097hz2dh2a8h839h93fhe5bhf0ah1288h12a5h12a9h12bdh137ah139eh13b6h1441h1504h1537h162dh1631h1758h1898h18e1h1946h19b5h1ad9h1b0ah1b2fh2222h224fh1fb3h1d0ch1d2eh1d3fh1dc1h1dfeh1dffh1e23h1fe8h1ff5h2218h2216h226dh22d0h24afh2327h2336h2438h2461h2487h24d7h2516h2545h255eh25cch25f6h2605h268bh26d3h1155h) Received: from mail64-am1 (localhost.localdomain [127.0.0.1]) by mail64-am1 (MessageSwitch) id 1397121670607852_21040; Thu, 10 Apr 2014 09:21:10 +0000 (UTC) Received: from AM1EHSMHS002.bigfish.com (unknown [10.3.201.242]) by mail64-am1.bigfish.com (Postfix) with ESMTP id 84EC84600EF; Thu, 10 Apr 2014 09:21:10 +0000 (UTC) Received: from mail.freescale.net (70.37.183.190) by AM1EHSMHS002.bigfish.com (10.3.207.102) with Microsoft SMTP Server (TLS) id 14.16.227.3; Thu, 10 Apr 2014 09:21:10 +0000 Received: from az84smr01.freescale.net (10.64.34.197) by 039-SN1MMR1-002.039d.mgd.msft.net (10.84.1.15) with Microsoft SMTP Server (TLS) id 14.3.174.2; Thu, 10 Apr 2014 09:21:30 +0000 Received: from victor.ap.freescale.net (victor.ap.freescale.net [10.192.241.62]) by az84smr01.freescale.net (8.14.3/8.14.0) with ESMTP id s3A9LQ43031344; Thu, 10 Apr 2014 02:21:27 -0700 From: Liu Ying To: Subject: [PATCH v2] pwm: i.MX: Avoid sample fifo overflow for i.MX pwm version2 Date: Thu, 10 Apr 2014 17:23:49 +0800 Message-ID: <1397121829-19331-1-git-send-email-Ying.Liu@freescale.com> X-Mailer: git-send-email 1.7.9.5 MIME-Version: 1.0 X-OriginatorOrg: freescale.com X-FOPE-CONNECTOR: Id%0$Dn%*$RO%0$TLS%0$FQDN%$TlsDn% X-FOPE-CONNECTOR: Id%0$Dn%FREESCALE.MAIL.ONMICROSOFT.COM$RO%1$TLS%0$FQDN%$TlsDn% X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20140410_052158_214012_FF7C6B3C X-CRM114-Status: GOOD ( 16.38 ) X-Spam-Score: -1.3 (-) Cc: linux-pwm@vger.kernel.org, s.hauer@pengutronix.de, linux-arm-kernel@lists.infradead.org, shawn.guo@freescale.com, LW@KARO-electronics.de X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-3.5 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD,UNPARSEABLE_RELAY,UNRESOLVED_TEMPLATE autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The i.MX pwm version2 is embedded in several i.MX SoCs, such as i.MX27, i.MX51 and i.MX6SL. There are four 16bit sample fifos in this IP, each of which determines the duty period of a PWM waveform in one full cycle. The IP spec mentions that we should not write a fourth sample because the fifo will become full and trigger a fifo write error(FWE) which will prevent the PWM from starting once it is enabled. In order to avoid any sample fifo overflow issue, this patch does software reset to clear all the sample fifos in the very beginning of the pwm configuration function. The fifo overflow issue can be reproduced by the following commands on the i.MX6SL evk platform, assuming we use pwm2 for the debug LED which is driven by the pin HSIC_STROBE and the maximal brightness is 255. echo 0 > /sys/class/leds/user/brightness echo 0 > /sys/class/leds/user/brightness echo 0 > /sys/class/leds/user/brightness echo 0 > /sys/class/leds/user/brightness echo 255 > /sys/class/leds/user/brightness Here, FWE happens(PWMSR register reads 0x58) and the LED can not be lighten. Cc: Sascha Hauer Cc: Shawn Guo Cc: Lothar Waßmann Cc: linux-pwm@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Signed-off-by: Liu Ying Acked-by: Shawn Guo --- v1->v2: * To address Lothar Waßmann's comment, add a timeout mechanism instead of endless polling the SWR bit to be cleared by the hardware. drivers/pwm/pwm-imx.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c index cc47733..8929b0d 100644 --- a/drivers/pwm/pwm-imx.c +++ b/drivers/pwm/pwm-imx.c @@ -14,6 +14,7 @@ #include #include #include +#include #include #include #include @@ -38,8 +39,11 @@ #define MX3_PWMCR_DBGEN (1 << 22) #define MX3_PWMCR_CLKSRC_IPG_HIGH (2 << 16) #define MX3_PWMCR_CLKSRC_IPG (1 << 16) +#define MX3_PWMCR_SWR (1 << 3) #define MX3_PWMCR_EN (1 << 0) +#define MX3_PWM_SWR_LOOP 5 + struct imx_chip { struct clk *clk_per; struct clk *clk_ipg; @@ -103,10 +107,23 @@ static int imx_pwm_config_v2(struct pwm_chip *chip, struct pwm_device *pwm, int duty_ns, int period_ns) { struct imx_chip *imx = to_imx_chip(chip); + struct device *dev = chip->dev; unsigned long long c; unsigned long period_cycles, duty_cycles, prescale; + int wait_count = 0; u32 cr; + /* do software reset in case fifo overflows */ + writel(MX3_PWMCR_SWR, imx->mmio_base + MX3_PWMCR); + do { + usleep_range(200, 1000); + cr = readl(imx->mmio_base + MX3_PWMCR); + } while ((cr & MX3_PWMCR_SWR) && + (wait_count++ < MX3_PWM_SWR_LOOP)); + + if (cr & MX3_PWMCR_SWR) + dev_warn(dev, "software reset timeout\n"); + c = clk_get_rate(imx->clk_per); c = c * period_ns; do_div(c, 1000000000);